Environmental regulations are becoming more stringent with a greater emphasis on the reduction of gaseous emissions from factories, especially volatile organic compounds which may include, for example, ethanol, acetone, isopropyl alcohol, heptanone, or triethanolamine. One example of current VOC abatement technology includes a VOC concentrator (absorber) coupled with a thermal oxidizer to burn the desorbent (regeneration) effluent gas, as shown in FIG. 1. A laboratory, or a factory 10 or other facility, typically includes extensive duct work used to collect localized hot air, gases, fumes or dust from process operations. Some process operations may be vented or filtered, some are enclosed or hooded to provide maximum collection efficiency.
The exhaust 13 from the factory 10 typically includes volatile organic compounds (VOCs) which are abated by being absorbed in regenerative absorbent apparatus 15 which may typically comprise slowly rotating drum devices, on which successive increments of zeolite beds absorb the VOCs and are subsequently desorbed, repetitively. Or the absorbent apparatus may comprise push/pull alternate beds in which one bed is absorbing while the other is being desorbed, and then the reverse occurs.
The output 17 of the regenerative VOC absorber 15 is clean air which is typically released to ambient. The effluent 20 from the desorption phase in the regenerative VOC absorber 15 is applied by a blower 21 over a conduit 22 to a burner 23 of a thermal oxidizer 24, which burns the vaporous regeneration effluent along with natural gas 25 and air 26 from a blower 28. The hot outflow of the burner 23 is passed through an oxidizer 31, the output 32 of which is partially released to ambient and partially mixed with fresh air 35 and applied to a blower 38. The blower output 40, applied to the desorption gas inlet 41 of the apparatus 15, is used as the desorption gas in the regenerative VOC adsorber 15.
The apparatus of FIG. 1 therefore utilizes natural gas simply to burn the VOC regenerative products.
While the apparatus of FIG. 1 is an adequate solution to meeting near-term permitted air standards, efficient, sustainable operations therewith are limited. Most of the heat generated by the natural gas passes to ambient in the clean exhaust 32. The pumping in of additional cooling air 35, 38 illustrates the waste of fuel.